Scrotal sac
In human males, the testes are situated outside the abdominal or pelvic cavity in a sac of skin called the scrotal sac. It acts as thermoregulation to keep the testicular temperature 2-3c lower than the optimum temperature necessary for sperm production (spermatogenesis). It is biologically homologous to the major in females.
Testes
These are the primary male gonads in man. Each testis is oval in shape, with a length of about 4-5 cm and a width of 2-3 cm. They develop in the scrotum by a spermatic cord in the later stages of life.
Cremaster muscles and dortas muscles of the scrotal sac help in the positioning of the testes. Whenever the temperature is low, these contract to move the testes close to the abdomen or pelvic cavity and vice-versa.
Note * Cremaster muscle and connective tissues surround all structures passing through the inguinal canal including the spermatic cord.
* If testes fail to descend, this condition is called cryptorchidism, which leads to sterility. inflammation of the testis is called orchitis.
* Gubernaculum is a fibrous cord that extends from the caudal end of the testis to the scrotal wall.
Tunica of testis
The testis is surrounded by three protective coverings known as tunicates. These are as follows:
(1) Tunica vaginalis It is the outer covering of the testes.
(2) Tunica albuginea It is the white fibrous capsule that sends partitions through its interior surface to divide the testis onto lobules.
(3) Tunica vasculosa contains a network of capillaries that are supported by delicate connective tissue.
Seminiferous tubules
Each testies has about 250 compartments called testicular lobules and each lobule contains one to three highly coiled seminiferous tubules, where the sperms are produced. Seminiferous tubules from loops at both ends, which continue as a short segment of straight tubules, the tubuli recti. These tubules connect the seminiferous tubules to a highly anastomosing labyrinth of cuboidal epithelium-lined channels, the rete testis, which gives rise to 10-12 fine tubules called ductules efferentes.
Tubuli recti, rete testis, and ductile efferentes from the intertentacular genital duct systems. the tubules of ductuli efferentes combine to form the ductus epididymis.
The stratified epithelium of the seminiferous tubule is made up of three types of cells.
(1) Sertoli cells (supporting cells) These are also called sustentacular cells or nurse cells. They are elongated and pyramidal, which partially envelope the spermatogenic cells. This cell secret a glycoprotein hormone called inhibin, which is involved in the negative feedback control of sperm production by checking FSH activity.
(2) Spermatogenic cells Line the space between the basal lamina and the lumen of the tubule. These cells divide several times and differentiate to produce spermatozoa.
(3) Leydig cells (interstitial cells) They are a group of polyhedral cells and are present between the seminiferous tubules.
These cells secrete the testosterone hormone that controls spermatogenesis. These are endocrine in nature and are a characteristics feature of the testes of mammals.
Vasa efferentia(Sing. vas efferens)
A set of about 10-20 vasa efferentia collects from inside the testis and transfers them to the epididymis through rete testis. It has large columnar ciliated cells and small non-ciliated cells with endocytic activity, which help in conducting sperms.
Epididymis
The epididymis is a coiled tube, which consists of three parts. The anterior end called caput epididymis, middle part corpse epididymis, and the posterior end is cauda epididymis. It is lined with pseudostratified columnar epithelium. It stores by sperm temporarily and produce essential chemicals required for the nourishment and maturation of sperms.
Vasa deferentia
It is a straight tube, which carries sperms to the urethra. Most of the sperms are stored in vas deferens. vas deferens is also called ductus deferens or sperm duct. It arises from cauda epididymis, ascends to the abdomen, passes over the urinary bladder, and receives the duct from the seminal vesicle behind the urinary bladder forming an ejaculatory duct. it passes through the prostate to open the ejaculatory duct. it passes through the prostate to open into the urethra shortly after its origin from the urinary bladder.
Urethra
It carries urine from the bladder as well as, sperms from the vas deferentia, through the penis. Thus, it is known as urinogenital as it provides a common pathway for the flow of both urine and semen.
It comprises three regions
(1) A short proximal prostatic urethra surrounded by the prostate gland.
(2) A very short middle membranous urethra without covering.
(3) A long distal penile urethra that passes through penis.
penis
It is male external genitalia. It is vascular, spongy contains erectile tissue and a pensile organ suspended from the public region in from public region in front of the scrotum. During sexual arousal, erectile tissue fills with blood, causing the penis to become hard and erect to facilitate copulation and transmit sperms into the vagina of the female. Therefore, it is also called a copulatory organ. it has a glance penis at the tip, which is covered with a loose fold of skin called the prepuce or foreskin. The margin of glance penis is known as Corona.
The interior of the penis consists of three cylindrical cords made of spongy and erectile tissue. Two of them are parallel and called corpora cavernosa, which become superior-posterior when the penis is erect. The third, spongiosum corpora urethrae remain inferior-anterior in an erect penis. It is called so because the urethra runs from this cord. The pineal mass is covered by a dense connective tissue,m called tunica albuginea. Tyson's gland or preputial gland present in the penis neck secret a white sebaceous substance called smegma.